Ten is mistakenly written by Tim in question. Gabriel is making a mixture of compost and soil. In which he wants to mix 2 part compost to 10 parts potting soil. And he wants to end up with ten kilogram It means compost is 2 pars out of 12 and potting soil is 10 parts out of 12 so, (2 / 12) x 10 kilogram of compost is used = 1.66667 kilogram of compost Gabriel should use.
